1. Field of the Invention
The present disclosure generally relates to assessing surface cleanliness. More particularly, the disclosure generally relates to a portable system and method for measuring a contact angle between a droplet of liquid and a surface.
2. Description of the Relevant Art
There are many instances where a surface must be cleaned sufficiently to permit a following operation to be conducted. For example, a surface that is to be coated (e.g., paint) must first have contaminants (e.g., oil, particulate matter, etc.) removed from the surface so that the coating to be applied will adhere properly to the surface. Proper surface cleanliness is especially important for a smooth metallic surface (e.g., planes, cars, trucks, etc.). Surface irregularities resulting from contamination minimizes coating adhesion through the keying action between the coating film and surface irregularities. Coating adhesion in such cases depends substantially on other adherent mechanisms such as molecular attraction between the metallic surface and the applied coating, and good molecular bonding is achieved only when the surface is properly free of contamination.
The cost of cleaning a surface to be painted increases when the surface being cleaned is part of a large assembled structure. While a surface can be deliberately cleaned beyond the minimum extent necessary for the desired coating adhesion, the expense of such excessive cleaning of the surface is counterproductive.
The measurement of contact angle began in 1805 with the work of Thomas Young. Since then there have been many papers published using contact angle or suggesting new ways to measure contact angle. Almost all of these methods are focused on small samples that may be brought to the lab for analysis in a contact angle measuring device. The field appropriate analyses are mainly the Bikerman method of viewing a drop from above, the Langmuir method of viewing the angle of reflected light from the drop surface, and the drop-shape analysis methods that view the drop from the side. All of these methods have been successfully used in the laboratory. The utility of this method has been revisited recently to show its compatibility and improvement with modern cell phone cameras, macro lenses, and computer spreadsheet programs. But to date, no known source exists that provides the various parts in a self-calibrating contact angle measurement kit that would enable the user to utilize these field-appropriate methods.